High-heat-resistant low-water-absorption reactive phosphorus-containing flame retardant, preparation method and application thereof

Abstract

The application relates to the technical field of halogen-free flame-retardant resins, in particular to a high-heat-resistance low-water-absorption reactive phosphorus-containing flame retardant as well as a preparation method and application thereof. The phosphorus-containing flame retardant has a molecular structure as shown in formula 1, wherein the R1 group comprises at least one of,,,,,,,,,, and ; the value of n satisfies 0 < n <= 50, and the value of n is an integer. The phosphorus-containing flame retardant is designed in multiple dimensions through a molecular structure, comprehensively improves the comprehensive performance of a copper-clad plate, and fundamentally solves the water absorption problem of a phosphorus-based flame retardant.

Description

Technical Field

[0001] This application relates to the field of halogen-free flame retardant resin technology, and in particular to a highly heat-resistant, low-water-absorption reactive phosphorus-containing flame retardant, its preparation method, and its application. Background Technology

[0002] With the rapid development of industries such as Artificial Intelligence Large Scale Integrated Circuits (AIGC), machine learning, 5G communication, millimeter-wave radar, and the Internet of Things, the frequency of signal transmission on printed circuit boards is increasing. This has made high-frequency, high-speed copper-clad laminates a research hotspot in the printed circuit board industry. To reduce transmission losses in high-frequency bands and meet the requirements of high-temperature soldering and multilayer assembly during substrate mounting, the insulating materials used to prepare copper-clad laminates need to possess halogen-free flame retardancy, superior dielectric properties, heat resistance, glass transition temperature, and dimensional stability.

[0003] Hydrocarbon resins have low molecular chain polarity (electronegativity of carbon and hydrogen atoms are 2.5 and 2.1, respectively), thus exhibiting excellent dielectric properties (dielectric constant of 2.4 to 2.8 and tanδ of 0.0002 to 0.0006 at 1 MHz). However, hydrocarbon resins have poor flame retardant properties, failing to meet the current requirements for halogen-free flame retardancy in copper-clad laminates used in electronic devices. Therefore, to improve the flame retardant properties of hydrocarbon resins, flame-retardant materials need to be added.

[0004] Currently, the flame retardant materials used in copper clad laminates are mainly phosphorus-based flame retardants. Although phosphorus-based flame retardants have advantages such as good compatibility, high stability, and high flame retardant performance, whether reactive or additive, the phosphorus-containing flame retardant groups (such as phosphorus-oxygen double bonds P=O) in these flame retardants are polar and easily combine with water molecules in the environment where the copper clad laminate is used through hydrogen bonds, which increases the absorption rate of the copper clad laminate and leads to a decrease in the dielectric properties of the copper clad laminate, resulting in a decrease in the performance of the copper clad laminate in high-frequency environments. Summary of the Invention

[0005] This application provides a highly heat-resistant, low-water-absorption reactive phosphorus-containing flame retardant, its preparation method, and its application, to solve the following technical problem: how to reduce the water absorption of phosphorus-based flame retardants while improving the flame retardant performance of copper-clad laminates.

[0006] In a first aspect, embodiments of this application provide a highly heat-resistant, low-water-absorption reactive phosphorus-containing flame retardant, wherein the phosphorus-containing flame retardant has a molecular structure as shown in Formula 1. , Formula 1, In Formula 1, the R1 group includes , , , , , , , , , , , , , and At least one of them; The value of n satisfies: 0 < n ≤ 50, and the value of n is an integer.

[0007] Optionally, the phosphorus content in the phosphorus-containing flame retardant is 6.3% to 9.1% by mass.

[0008] Secondly, embodiments of this application provide a method for preparing the phosphorus-containing flame retardant described in the first aspect, the method comprising: Phosphorus oxychloride, an acid-binding agent, and a first organic solvent are mixed to obtain the reaction raw materials; The bisphenol compound, 2,4-dimethyl-3-hydroxybenzocyclobutene, catalyst and the reactants were subjected to a polymerization reaction to obtain the reaction product; The reaction product was washed with pure water to obtain a washed product; The washing product was subjected to vacuum distillation to obtain a phosphorus-containing flame retardant.

[0009] Optionally, the amount of the phosphorus-containing compound n1 and the amount of the acid-binding agent n2 satisfy: n1:n2 = 1:(3.05 to 4.50); ​​and / or The amount of the catalyst n3 and the amount of the phosphorus-containing compound n1 satisfy: n3:n1 = (0.01 to 10.00):1; and / or The molar amounts n4 of the bisphenol compound and n5 of the 2,4-dimethyl-3-hydroxybenzocyclobutene satisfy: n4:n5 = (0.35 to 0.80):(1.6 to 2.3); and / or The mass m1 of the first organic solvent, the mass m2 of the phosphorus-containing compound, the mass m3 of the bisphenol compound, and the mass m4 of the 2,4-dimethyl-3-hydroxybenzocyclobutene satisfy the following: m1:(m2+m3+m4)=(2.5 to 6):1.

[0010] Optionally, the acid-binding agent includes at least one of sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, sodium bicarbonate, potassium bicarbonate, tetrahydrofuran, trimethylamine, triethylamine, sodium acetate, and potassium acetate; and / or The bisphenol compounds include at least one selected from hydroquinone, resorcinol, bisphenol A, bisphenol C, bisphenol F, tetramethylbisphenol A, tetramethylbisphenol F, 4,4'-dihydroxybiphenyl, tetramethylbiphenyl, hexamethylbiphenyl, 1,5-naphthoquinone, 1,4-dihydroxynaphthol, and 1,6-dihydroxynaphthol; and / or The first organic solvent includes at least one of toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexane, and n-hexane; and / or The catalysts include at least one of the following: tetrabutylammonium bromide, benzyltriethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, crown ether, polyethylene glycol, acetonitrile, N,N'-dimethylformamide, and N,N'-dimethylacetamide.

[0011] Optionally, the polymerization reaction is carried out at a temperature of 50°C to 60°C for a duration of 8 to 12 hours; and / or The temperature of the early mixing stage of the polymerization reaction is ≤45℃.

[0012] Thirdly, embodiments of this application provide an application of the phosphorus-containing flame retardant described in the first aspect in copper-clad laminates. The raw materials of the copper-clad laminate, by mass parts, include: polyolefin resin: 55 to 73 parts, the phosphorus-containing flame retardant described in the first aspect: 27 to 45 parts, initiator: 0.03 to 0.25 parts, and filler: 45 to 60 parts; wherein the sum of the mass parts of the polyolefin resin and the phosphorus-containing flame retardant is 100.

[0013] Optionally, the method for preparing the copper-clad laminate includes: The polyolefin resin, the phosphorus-containing flame retardant, the initiator, and the filler are mixed in a second organic solvent to obtain a resin solution; Glass fibers are sequentially impregnated and suspended in the resin solution to obtain flame-retardant glass fiber cloth. The flame-retardant treated glass fiber cloth is baked to obtain a halogen-free flame-retardant semi-cured sheet. The halogen-free flame-retardant semi-cured sheets are stacked to obtain a laminated material; Copper foil is attached to both sides of the laminate to obtain a copper-clad laminate.

[0014] Optionally, the baking temperature is 130°C to 170°C, and the baking time is 4 min to 7 min; and / or The lamination process includes a pressurization section, a vacuum pressing section, and a hot pressing section. The final pressure of the pressurization section is 0.2 MPa to 4.0 MPa. The vacuum degree of the vacuum pressing section is ≤50 torr, and the vacuum pressing time is 0.5 h to 1.0 h. The temperature of the hot pressing section is 200 °C to 220 °C, and the hot pressing time is 4 h to 8 h.

[0015] Optionally, the polyolefin resin may include at least one of the following: butadiene polymer, butadiene-styrene copolymer, butadiene-styrene-monobutene terpolymer, divinylbenzene polymer, and divinylbenzene-monobutene copolymer; and / or The initiator includes at least one of dicumyl peroxide, di-tert-butyl peroxide, and tert-butyl peroxide; and / or The filler material includes at least one of the following: silica, montmorillonite, magnesium oxide, aluminum oxide, mica powder, barium sulfate, kaolin, silicon nitride, boron nitride, zirconium oxide, aluminum nitride, graphite, titanium dioxide, talc, and iron oxide; and / or The second organic solvent includes at least one of acetone, butanone, cyclohexanone, methyl isobutyl ketone, toluene, propylene glycol monomethyl ether, and propylene glycol methyl ether acetate.

[0016] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a high-heat-resistant, low-water-absorption reactive phosphorus-containing flame retardant. Through a specific molecular structure design, this flame retardant introduces a large number of methyl-substituted benzene ring structures. These methyl groups can form a dense steric barrier around the phosphorus oxide group, thereby reducing the overall polarity of the flame retardant and decreasing its water absorption. Furthermore, this flame retardant contains at least four benzocyclobutenyl groups, which can chemically react with the polyolefin resin of the copper-clad laminate, participating in the construction of a three-dimensional cross-linked network of the resin. This effectively inhibits the migration and precipitation of the flame retardant, improving the heat resistance and dimensional stability of the copper-clad laminate. Simultaneously, the introduction of rigid hydrophobic aromatic structures such as benzene rings, biphenyl rings, and naphthalene rings into the main chain and R1 group of the phosphorus-containing flame retardant further enhances the compatibility between the phosphorus-containing flame retardant and the polyolefin resin, increases the glass transition temperature, and thus improves the heat resistance, dimensional stability, and mechanical properties of the phosphorus-containing flame retardant. In addition, the phosphorus-containing flame retardant has a high phosphorus content. During combustion, the phosphorus will decompose efficiently and release acidic substances such as phosphoric acid and metaphosphoric acid, which catalyze the dehydration and carbonization of the resin in the copper-clad laminate to form a dense carbon layer, further improving the heat resistance of the copper-clad laminate. At the same time, the high phosphorus content reduces the introduction of polar groups, avoiding the problem of increased water absorption caused by excessive addition of polar groups. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic flowchart of a method for preparing a phosphorus-containing flame retardant provided in an embodiment of this application; Figure 2 This is a schematic diagram of the process for preparing the copper-clad laminate provided in the embodiments of this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] The range descriptions used in this application, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "comprising" and others used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships involved in this document, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained by purchasing from the market or by existing methods.

[0022] This application provides a highly heat-resistant, low-water-absorption reactive phosphorus-containing flame retardant, wherein the phosphorus-containing flame retardant has the molecular structure shown in Formula 1. , Formula 1, In Formula 1, the R1 group includes , , , , , , , , , , , , , and At least one of them; The value of n satisfies: 0 < n ≤ 50, and the value of n is an integer.

[0023] It should be noted that the core problem of traditional phosphorus-based flame retardants is that the core flame-retardant group (phosphooxy group P=O, PO) is a strongly polar hydrophilic group, which readily forms hydrogen bonds with water molecules, resulting in high water absorption. Furthermore, to meet flame-retardant requirements, a high dosage is often required, further exacerbating the water absorption of traditional phosphorus-based flame retardants. This deteriorates the heat resistance, dielectric properties, and dimensional stability of copper-clad laminates, creating a vicious cycle of "flame retardant improvement → performance degradation." However, the embodiments of this application provide a highly heat-resistant, low-water-absorption reactive phosphorus-containing flame retardant. This phosphorus-containing flame retardant, through multi-dimensional synergistic design of its molecular structure, comprehensively improves the overall performance of copper-clad laminates while fundamentally solving the water absorption problem of phosphorus-based flame retardants. The specific mechanism is as follows: I. Spatial steric damming design: blocks the absorption of water by phosphorus oxides at the source without sacrificing flame retardant efficiency.

[0024] 1. Structural design: In this phosphorus-containing flame retardant molecule, the phosphorus group is surrounded by a large number of methyl-substituted benzene ring structures. The methyl groups form a dense steric barrier around the polar phosphorus group, which is equivalent to adding a hydrophobic protective shield to the hydrophilic phosphorus group.

[0025] 2. Buff Effect: (1) Reduced water absorption: The hydrophobic protective shield formed can significantly reduce the overall polarity of the molecule, directly blocking the possibility of phosphorus groups forming hydrogen bonds with water molecules, thus solving the hydrophilicity problem of phosphorus groups from the source of the molecule. (2) Improved performance: The phosphorus content of this phosphorus-containing flame retardant remains at a high level. During combustion, it can still efficiently decompose and release acidic substances such as phosphoric acid and metaphosphoric acid to catalyze the dehydration and carbonization of the resin used in copper-clad laminates to form a dense carbon layer. Only a small amount of addition is needed to make the copper-clad laminate reach the UL94 V0 flame retardant level. No high addition amount is required, which further reduces the introduction of polar groups and avoids the problem of increased water absorption caused by traditional high addition amounts.

[0026] II. Multi-reactive cross-linking design: Eliminates interfacial water absorption channels while locking in flame retardant stability and improving heat resistance.

[0027] 1. Structural design: The phosphorus-containing flame retardant molecules have four or more benzocyclobutene reactive groups, which can chemically react with the unsaturated polyolefin resin used in copper clad laminates and become part of the resin's three-dimensional cross-linked network, rather than being a traditional physical additive.

[0028] 2. Buff Effect: (1) Reduced water absorption: It completely avoids the migration and precipitation problems of traditional additive phosphorus flame retardants, and eliminates the water molecule penetration channels such as interface voids and microcracks caused by the migration of phosphorus flame retardants; at the same time, it forms a dense cross-linked network, which further blocks the water molecule penetration path and reduces the water absorption rate from the overall system level. (2) Improved performance: The phosphorus-containing flame retardant forms an integrated cross-linked structure with the polyolefin resin, and the flame retardant performance is stable for a long time without decay; at the same time, the cross-linked network greatly improves the heat resistance and dimensional stability of the cured product, reduces the microcracks caused by dimensional deformation at high temperature, avoids the risk of secondary water absorption, and achieves the synergistic effect of improving the heat resistance and reducing the water absorption of the copper clad laminate.

[0029] III. Rigid hydrophobic aromatic skeleton: further reduces molecular polarity while enhancing heat resistance and dielectric properties.

[0030] 1. Structural design: The phosphorus-containing flame retardant molecule introduces a large number of rigid hydrophobic aromatic structures such as benzene rings, biphenyl rings, and naphthalene rings into the main chain and R1 group, without additional hydrophilic polar groups, thus constructing a hydrophobic framework for the entire molecule.

[0031] 2. Buff Effect: (1) Reduced water absorption: The aromatic hydrophobic skeleton further reduces the overall polarity of the molecules, which is highly matched with the polarity of the low polarity polyolefin resin used in copper clad laminates. It has excellent compatibility and completely avoids the phase separation and interface defects between traditional polar flame retardants and non-polar resins, thus fundamentally eliminating the core hidden danger of water absorption at the interface of copper clad laminates. (2) Improved performance: The rigid aromatic structure of phosphorus flame retardant significantly improves the glass transition temperature (Tg can be as high as 244℃ to 263℃), dimensional stability and mechanical properties of the resin cured product. At the same time, the low polarity uniform system gives the copper clad laminate excellent high-frequency dielectric properties, making the dielectric constant of the copper clad laminate as low as 2.59 to 2.67 and the dielectric loss as low as 0.0010 to 0.0011 at 10GHz, which perfectly meets the needs of high-frequency and high-speed signal transmission.

[0032] In summary, the embodiments of this application provide a high heat-resistant, low water-absorption reactive phosphorus-containing flame retardant. This phosphorus-containing flame retardant, through a triple molecular design of "steric hindrance shielding hydrophilic groups + reactive cross-linking locking system + hydrophobic skeleton reducing polarity," completely breaks the contradiction of "the trade-off between flame retardancy and water absorption, heat resistance, and dielectric properties" that exists in traditional phosphorus-based flame retardants. Ultimately, it achieves a comprehensive improvement in the performance of copper-clad laminates: flame retardancy reaches UL94 V0 level, high heat resistance and high dimensional stability, excellent high-frequency dielectric properties, while the water absorption rate is as low as 0.05% to 0.08%, perfectly solving the water absorption problem of phosphorus-based flame retardants.

[0033] In some alternative embodiments, the phosphorus-containing flame retardant has a phosphorus content of 6.3% to 9.1% by mass.

[0034] In these embodiments, the presence of 6.3% to 9.1% phosphorus by mass in the phosphorus-containing flame retardant indicates that the phosphorus-containing flame retardant has a large amount of phosphorus. This phosphorus can efficiently decompose and release acidic substances such as phosphoric acid and metaphosphoric acid during the heated combustion stage of the copper-clad laminate, thereby catalyzing the dehydration and carbonization of the resin used in the copper-clad laminate to form a dense carbon layer, enabling the copper-clad laminate to achieve the UL94 V0 flame retardant level.

[0035] The phosphorus content in this phosphorus-containing flame retardant can be 6.3%, 6.4%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, or 9.1%.

[0036] Figure 1 An exemplary schematic diagram of a method for preparing a phosphorus-containing flame retardant provided in an embodiment of this application is shown; Based on a general inventive concept, such as Figure 1 As shown in the embodiments of this application, a method for preparing the phosphorus-containing flame retardant is provided, the method comprising: S1. Phosphorus oxychloride, acid-binding agent and first organic solvent are mixed to obtain the reaction raw materials; S2. The bisphenol compound, 2,4-dimethyl-3-hydroxybenzocyclobutene, catalyst and the reactants are subjected to a polymerization reaction to obtain the reaction product; S3. Wash the reaction product with pure water to obtain a washed product; S4. The washing product is subjected to vacuum distillation to obtain a phosphorus-containing flame retardant.

[0037] This method is for the preparation of the phosphorus-containing flame retardant mentioned above. Specific information about the phosphorus-containing flame retardant can be found in the above embodiments. Since this method adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0038] It should be noted that the raw material addition stage of this method, such as mixing and polymerization reaction, is carried out under a nitrogen atmosphere. In addition, in the early stage of the polymerization reaction, the bisphenol compound and 2,4-dimethyl-3-hydroxybenzocyclobutene (monophenol compound) are added to the reaction raw materials together and stirred for 1 to 2 hours to ensure that the bisphenol compound, monophenol compound and reaction raw materials are mixed evenly. The addition stage is carried out under water bath conditions to control the temperature below 45°C and avoid excessive temperature fluctuations that may affect the activity of the raw materials.

[0039] In some optional embodiments, the amount n1 of the phosphorus-containing compound and the amount n2 of the acid-binding agent satisfy: n1:n2 = 1:(3.05 to 4.50); ​​and / or The amount of the catalyst n3 and the amount of the phosphorus-containing compound n1 satisfy: n3:n1 = (0.01 to 10.00):1; and / or The molar amounts n4 of the bisphenol compound and n5 of the 2,4-dimethyl-3-hydroxybenzocyclobutene satisfy: n4:n5 = (0.35 to 0.80):(1.6 to 2.3); and / or The mass m1 of the first organic solvent, the mass m2 of the phosphorus-containing compound, the mass m3 of the bisphenol compound, and the mass m4 of the 2,4-dimethyl-3-hydroxybenzocyclobutene satisfy the following: m1:(m2+m3+m4)=(2.5 to 6):1.

[0040] In these embodiments, the molar ratio of a phosphorus-containing compound and an acid-binding agent of 1:(3.05 to 4.50), the molar ratio of a catalyst and a phosphorus-containing compound of (0.01 to 10.00):1, and the molar ratio of a bisphenol compound and 2,4-dimethyl-3-hydroxybenzocyclobutene of (0.35 to 0.80):(1.6 to 2.3) allow the polymerization reaction to proceed sufficiently to form a phosphorus-containing flame retardant product having the molecular structure of Formula 1. Furthermore, a first organic solvent with a mass ratio of (2.5 to 6):1 to the sum of the masses of the phosphorus-containing compound, the bisphenol compound, and 2,4-dimethyl-3-hydroxybenzocyclobutene allows for sufficient polymerization between the catalyst, the phosphorus-containing compound, the bisphenol compound, and 2,4-dimethyl-3-hydroxybenzocyclobutene to form a phosphorus-containing flame retardant product having the molecular structure of Formula 1.

[0041] The amount of the acid-binding agent, n2, can be 3.05, 3.15, 3.20, 3.25, 3.30, 3.40, 3.50, 4.00, or 4.50.

[0042] The amount of the catalyst, n3, can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.10, 0.20, 0.30, 0.40, 0.50, 1.00, 2.00, 3.00, 4.00, 5.00, 6.00, 7.00, 8.00, 9.00, or 10.00.

[0043] The molar amount n4 of the bisphenol compound can be 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75 or 0.80.

[0044] The molar amount n5 of the 2,4-dimethyl-3-hydroxybenzocyclobutene can be 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4 or 2.5.

[0045] The mass m1 of the first organic solvent can be 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5 or 6.0.

[0046] In some alternative embodiments, the phosphorus-containing compound includes at least one of phosphorus oxychloride, phenylphosphine dichloride, and phenyl dichlorophosphate; and / or The acid-binding agent includes at least one of sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, sodium bicarbonate, potassium bicarbonate, tetrahydrofuran, trimethylamine, triethylamine, sodium acetate, and potassium acetate; and / or The bisphenol compounds include at least one selected from hydroquinone, resorcinol, bisphenol A, bisphenol C, bisphenol F, tetramethylbisphenol A, tetramethylbisphenol F, 4,4'-dihydroxybiphenyl, tetramethylbiphenyl, hexamethylbiphenyl, 1,5-naphthodin, 1,4-dihydroxynaphthol, and 1,6-dihydroxynaphthol; and / or The first organic solvent includes at least one of toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexane, and n-hexane; and / or The catalysts include at least one of the following: tetrabutylammonium bromide, benzyltriethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, crown ether, polyethylene glycol, acetonitrile, N,N'-dimethylformamide, and N,N'-dimethylacetamide.

[0047] In these embodiments, an acid-binding agent comprising at least one of sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, sodium bicarbonate, potassium bicarbonate, tetrahydrofuran, trimethylamine, triethylamine, sodium acetate, and potassium acetate is used; at least one of hydroquinone, resorcinol, bisphenol A, bisphenol C, bisphenol F, tetramethylbisphenol A, tetramethylbisphenol F, 4,4'-dihydroxybiphenyl, tetramethylbiphenyl, hexamethylbiphenyl, 1,5-naphthoquinone, 1,4-dihydroxynaphthyl, and 1,6-dihydroxynaphthyl is used as a bisphenol compound; and tetrabutylammonium bromide is used. At least one of benzyltriethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, crown ether, polyethylene glycol, acetonitrile, N,N'-dimethylformamide, and N,N'-dimethylacetamide is used as a catalyst, and at least one of toluene, xylene, butanone, methyl isobutyl ketone, cyclohexane, and n-hexane is used as a first organic solvent, such that the catalyst, phosphorus-containing compound, bisphenol compound, and 2,4-dimethyl-3-hydroxybenzocyclobutene undergo a sufficient polymerization reaction in the first organic solvent to form a phosphorus-containing flame retardant product having the molecular structure of Formula 1.

[0048] In some optional embodiments, the polymerization reaction is carried out at a temperature of 50°C to 60°C for a duration of 8 to 12 hours; and / or The temperature of the early mixing stage of the polymerization reaction is ≤45℃.

[0049] In these embodiments, polymerization at a temperature of 50°C to 60°C and a time of 8 to 12 hours allows the catalyst, phosphorus-containing compound, bisphenol compound, and 2,4-dimethyl-3-hydroxybenzocyclobutene to fully polymerize in the first organic solvent to form a phosphorus-containing flame retardant product having the molecular structure of Formula 1. Furthermore, the initial mixing stage of the polymerization reaction at a temperature ≤45°C ensures thorough mixing of the bisphenol compound, monophenol compound, and reactants, preventing material loss due to excessive temperature fluctuations.

[0050] The polymerization reaction can be carried out at temperatures of 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, or 60°C.

[0051] The polymerization reaction can be carried out for 8 hours, 8.5 hours, 9.0 hours, 9.5 hours, 10.0 hours, 10.5 hours, 11.0 hours, 11.5 hours, or 12.0 hours.

[0052] Based on a general inventive concept, this application provides an application of the phosphorus-containing flame retardant in copper-clad laminates. By mass, the raw materials of the copper-clad laminate include: polyolefin resin: 55 to 73 parts, the phosphorus-containing flame retardant: 27 to 45 parts, initiator: 0.03 to 0.25 parts, and filler: 45 to 60 parts; wherein, the sum of the mass parts of the polyolefin resin and the phosphorus-containing flame retardant is 100.

[0053] This application is based on the aforementioned phosphorus-containing flame retardant. Specific information about the phosphorus-containing flame retardant can be found in the above embodiments. Since this application adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0054] It should be noted that the mass fraction of polyolefin resin is 55 to 73 parts, and the mass fraction of phosphorus-containing flame retardant is 27 to 45 parts, with the sum of the mass fractions of polyolefin resin and phosphorus-containing flame retardant fixed at 100 parts. This precisely balances the intrinsic properties of the matrix with the flame retardant requirements. This approach ensures the core advantages of polyolefin resin—low dielectric strength, low water absorption, and high crosslinking—while maintaining a stable UL94 V0 flame retardant rating through the appropriate amount of flame retardant added. This avoids performance degradation caused by excessive flame retardant addition and allows for precise control of the crosslinking density and polarity matching of the copper-clad laminate system, ensuring batch-to-batch performance stability. The initiator, at a mass fraction of 0.03 to 0.25 parts, efficiently triggers the crosslinking reaction between the polyolefin resin and the phosphorus-containing flame retardant, forming a dense and uniform three-dimensional network. It also avoids the degradation of small molecule residues, dielectric strength, and water resistance caused by excessive initiator. In addition, fillers with a mass fraction of 45 to 60 parts can significantly improve the dimensional stability, heat resistance, and rigidity of copper clad laminates, reduce the coefficient of thermal expansion of copper clad laminates, and at the same time, will not cause a decrease in processing performance or a deterioration in dielectric properties due to excessive fillers. They also have excellent compatibility with the host system and synergistically optimize the overall performance of copper clad laminates.

[0055] The mass fraction of the polyolefin resin can be 55, 56, 57, 58, 59, 60, 65, 70, 71, 72, or 73 parts.

[0056] The mass fractions of phosphorus-containing flame retardants can be 27, 28, 29, 30, 31, 32, 33, 34, 35, 40, or 45.

[0057] The mass fraction of the initiator can be 0.03 parts, 0.04 parts, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, 0.10 parts, 0.15 parts, 0.20 parts, or 0.25 parts.

[0058] The mass fraction of the filler can be 45, 46, 47, 48, 49, 50, 55 or 60 parts.

[0059] Figure 2 A schematic diagram illustrating the process flow of the copper-clad laminate preparation method provided in this application embodiment is shown as an example; In some alternative implementations, such as Figure 2 As shown, the method for preparing the copper-clad laminate includes: S1. The polyolefin resin, the phosphorus-containing flame retardant, the initiator, and the filler are mixed in a second organic solvent to obtain a resin solution; S2. Glass fibers are sequentially impregnated and suspended in the resin solution to obtain flame-retardant glass fiber cloth; S3. Bake the flame-retardant treated glass fiber cloth to obtain a halogen-free flame-retardant semi-cured sheet; S4. Stack the halogen-free flame-retardant semi-cured sheets to obtain a laminate; S5. Attach copper foil to both sides of the laminate to obtain a copper-clad laminate.

[0060] In these embodiments, polyolefin resin, phosphorus-containing flame retardant, initiator, and filler are first mixed in a second organic solvent to obtain a homogeneous resin solution. Then, glass fiber cloth is impregnated in the resin solution to ensure uniform distribution of the resin solution on the glass fiber cloth. Excess second organic solvent in the glass fiber is then dissipated by gravity through suspension. Furthermore, baking promotes the reaction between the polyolefin resin and phosphorus-containing flame retardant in the glass fiber cloth under the action of the initiator, and cures the filler to form a flowing adhesive, thus forming a halogen-free flame-retardant semi-cured sheet. Finally, by stacking the halogen-free flame-retardant semi-cured sheets and attaching copper foil, a laminated copper-clad laminate product can be obtained.

[0061] It should be noted that the type of fiberglass cloth can be 1080E type fiberglass cloth, 2116 type fiberglass cloth, 2313 type fiberglass cloth, 3313 type fiberglass cloth or 7628 type fiberglass cloth.

[0062] In some optional embodiments, the baking temperature is 130°C to 170°C, and the baking time is 4 min to 7 min; and / or The lamination process includes a pressurization section, a vacuum pressing section, and a hot pressing section. The final pressure of the pressurization section is 0.2 MPa to 4.0 MPa. The vacuum degree of the vacuum pressing section is ≤50 torr, and the vacuum pressing time is 0.5 h to 1.0 h. The temperature of the hot pressing section is 200 °C to 220 °C, and the hot pressing time is 4 h to 8 h.

[0063] In these embodiments, baking at a temperature of 130°C to 170°C for 4 to 7 minutes allows the polyolefin resin in the fiberglass cloth to react with the phosphorus-containing flame retardant under the action of the initiator, and to cure the filler, forming a uniformly dispersed halogen-free flame-retardant semi-cured sheet. Furthermore, the pressurization stage with a final pressure of 0.2 MPa to 4.0 MPa allows excess adhesive in the halogen-free flame-retardant semi-cured sheet to be squeezed out, which is beneficial for fixing multilayer halogen-free flame-retardant semi-cured sheets. Additionally, vacuum pressing with a vacuum degree ≤ 50 torr and a time of 0.5 to 1.0 h removes air from different halogen-free flame-retardant semi-cured sheets while squeezing out the adhesive, which is beneficial for obtaining a closed stack. Finally, hot pressing at a temperature of 200°C to 220°C for 4 to 8 h allows different halogen-free flame-retardant semi-cured sheets to cure rapidly, forming a fixed stacked product.

[0064] The baking temperature can be 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃ or 170℃.

[0065] The baking time can be 4 min, 4.5 min, 5.0 min, 5.5 min, 6 min, 6.5 min, or 7.0 min.

[0066] The final pressure of this pressurization section can be 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa, 1.0MPa, 1.5MPa, 2.0MPa, 2.5MPa, 3.0MPa, 3.5MPa or 4.0MPa.

[0067] The vacuum pressing time can be 0.5h, 0.6h, 0.7h, 0.8h, 0.9h or 1.0h.

[0068] The temperature of the hot pressing section can be 200℃, 201℃, 202℃, 203℃, 204℃, 205℃, 210℃, 215℃ or 220℃.

[0069] The hot pressing time can be 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h or 8h.

[0070] In some alternative embodiments, the polyolefin resin includes at least one of the following: butadiene polymer, butadiene-styrene copolymer, butadiene-styrene-monobutene terpolymer, divinylbenzene polymer, and divinylbenzene-monobutene copolymer; and / or The initiator includes at least one of dicumyl peroxide, di-tert-butyl peroxide, and tert-butyl peroxide; and / or The filler material includes at least one of the following: silica, montmorillonite, magnesium oxide, aluminum oxide, mica powder, barium sulfate, kaolin, silicon nitride, boron nitride, zirconium oxide, aluminum nitride, graphite, titanium dioxide, talc, and iron oxide; and / or The second organic solvent includes at least one of acetone, butanone, cyclohexanone, methyl isobutyl ketone, toluene, propylene glycol monomethyl ether, and propylene glycol methyl ether acetate.

[0071] In these embodiments, the use of a polyolefin resin comprising at least one of butadiene polymer, butadiene-styrene copolymer, butadiene-styrene-monobutylene terpolymer, divinylbenzene polymer, and divinylbenzene-monobutylene copolymer, an initiator comprising at least one of dicumyl peroxide, di-tert-butyl peroxide, and tert-butyl peroxide, and a filler comprising at least one of silica, montmorillonite, magnesium oxide, aluminum oxide, mica powder, barium sulfate, kaolin, silicon nitride, boron nitride, zirconium oxide, aluminum nitride, graphite, titanium dioxide, talc, and iron oxide allows for a sufficient reaction between the polyolefin resin and the phosphorus-containing flame retardant under the action of the initiator. The use of a second organic solvent comprising at least one of acetone, butanone, cyclohexanone, methyl isobutyl ketone, toluene, propylene glycol monomethyl ether, and propylene glycol methyl ether acetate effectively disperses the polyolefin resin, the phosphorus-containing flame retardant, and the initiator, facilitating curing and molding during the baking stage.

[0072] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national / industry standards; if there is no corresponding national / industry standard, they are performed according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0073] Example 1

[0074] like Figure 1 As shown, a method for preparing the phosphorus-containing flame retardant includes: S1. A phosphorus-containing compound, an acid-binding agent, and a first organic solvent are mixed to obtain the reaction raw materials; S2. A polymerization reaction is carried out on bisphenol compound, 2,4-dimethyl-3-hydroxybenzocyclobutene, catalyst and reactants to obtain the reaction product; S3. Wash the reaction product with pure water until pH=7 to obtain the washed product; S4. The washing product is subjected to vacuum distillation to obtain a phosphorus-containing flame retardant.

[0075] The phosphorus content in the phosphorus-containing flame retardant is 7.33% by mass.

[0076] The amount of phosphorus-containing compound n1 and the amount of acid-binding agent n2 satisfy: n1:n2 = 1 mol: 1.6 mol; The amount of catalyst n3 and the amount of phosphorus-containing compound n1 satisfy the following: n3:n1=0.013mol:1mol; based on the mass of 1mol of phosphorus-containing compound being 153.3 parts by mass, the mass of the catalyst is 4.3 parts by mass.

[0077] The amounts of bisphenol compound n4 and 2,4-dimethyl-3-hydroxybenzocyclobutene n5 satisfy the following ratio: n4:n5 = 0.37 mol: 2.26 mol; The mass m1 of the first organic solvent, the mass m2 of the phosphorus-containing compound, the mass m3 of the bisphenol compound, and the mass m4 of 2,4-dimethyl-3-hydroxybenzocyclobutene satisfy the following condition: m1:(m2+m3+m4)=1540:(153.3+40.7+362.1).

[0078] The phosphorus-containing compound is phosphorus oxychloride; The acid-binding agent is triethylamine; The type of bisphenol compound is resorcinol; The first organic solvent is toluene; The catalyst is tetrabutylammonium bromide.

[0079] The polymerization reaction was carried out at a temperature of 55℃ for 9 hours. The temperature of the initial mixing stage of the polymerization reaction is ≤45℃, and the stirring time of the initial mixing stage is 1h.

[0080] The phosphorus-containing flame retardant has the molecular structure shown in Formula 1. , Formula 1, In Formula 1, the R1 group is ; The value of n satisfies: 0 < n ≤ 15, and the value of n is an integer.

[0081] Example 2

[0082] Compared to Example 1, the differences in this example are as follows, while the rest are the same: The phosphorus content in the phosphorus-containing flame retardant is 7.29% by mass.

[0083] The amount of phosphorus-containing compound n1 and the amount of acid-binding agent n2 satisfy: n1:n2 = 1 mol: 4.00 mol; The amount of catalyst n3 and the amount of phosphorus-containing compound n1 satisfy the following: n3:n1=6.84mol:1mol; with 1mol of phosphorus-containing compound having a mass of 153.3 parts by mass, the mass of the catalyst is 500 parts by mass.

[0084] The molar amounts of bisphenol compound n4 and 2,4-dimethyl-3-hydroxybenzocyclobutene n5 satisfy the following ratio: n4:n5 = 0.50 mol: 2.0 mol; The mass m1 of the first organic solvent, the mass m2 of the phosphorus-containing compound, the mass m3 of the bisphenol compound, and the mass m4 of 2,4-dimethyl-3-hydroxybenzocyclobutene satisfy the following condition: m1:(m2+m3+m4)=1700:(153.3+80.1+320.4).

[0085] The phosphorus-containing compound is phosphorus oxychloride; The acid-binding agent is potassium acetate; The type of bisphenol compound is 1,6-dihydroxynaphthalene; The first organic solvent is toluene; The catalyst is N,N'-dimethylformamide.

[0086] The polymerization reaction was carried out at a temperature of 58°C for 10 hours.

[0087] The phosphorus-containing flame retardant has the molecular structure shown in Formula 1. , Formula 1, In Formula 1, the R1 group is ; The value of n satisfies: 0 < n ≤ 22, and the value of n is an integer.

[0088] Example 3

[0089] Compared to Example 1, the differences in this example are as follows, while the rest are the same: The phosphorus content in the phosphorus-containing flame retardant is 7.28% by mass.

[0090] The amount of phosphorus-containing compound n1 and the amount of acid-binding agent n2 satisfy: n1:n2 = 1 mol: 3.90 mol; The amount of catalyst n3 and the amount of phosphorus-containing compound n1 satisfy the following: n3:n1=1.37mol:1mol; with 1mol of phosphorus-containing compound having a mass of 153.3 parts by mass, the mass of the catalyst is 100 parts by mass.

[0091] The amount of substance n4 of the bisphenol compound and the amount of substance n5 of 2,4-dimethyl-3-hydroxybenzocyclobutene satisfy the following: n4:n5 = 0.60 mol: 1.80 mol; The mass m1 of the first organic solvent, the mass m2 of the phosphorus-containing compound, the mass m3 of the bisphenol compound, and the mass m4 of 2,4-dimethyl-3-hydroxybenzocyclobutene satisfy the following: m1:(m2+m3+m4)=1800:(153.3+111.7+288.4).

[0092] The phosphorus-containing compound is phosphorus oxychloride; The acid-binding agent is trimethylamine; The type of bisphenol compound is 1,4-dihydroxybiphenyl; The first organic solvent is toluene; The catalyst is N,N'-dimethylformamide.

[0093] The polymerization reaction was carried out at a temperature of 60℃ for 11 hours.

[0094] The phosphorus-containing flame retardant has the molecular structure shown in Formula 1. , Formula 1, In Formula 1, the R1 group is ; The value of n satisfies: 0 < n ≤ 25, and the value of n is an integer.

[0095] Example 4

[0096] Compared to Example 1, the differences in this example are as follows, while the rest are the same: The phosphorus content in the phosphorus-containing flame retardant is 9.06% by mass.

[0097] The amount of phosphorus-containing compound n1 and the amount of acid-binding agent n2 satisfy: n1:n2 = 1 mol: 3.90 mol; The amount of catalyst n3 and the amount of phosphorus-containing compound n1 satisfy the following: n3:n1=1.37mol:1mol; with 1mol of phosphorus-containing compound having a mass of 153.3 parts by mass, the mass of the catalyst is 100 parts by mass.

[0098] The amount of substance n4 of the bisphenol compound and the amount of substance n5 of 2,4-dimethyl-3-hydroxybenzocyclobutene satisfy the following: n4:n5 = 0.80 mol: 1.40 mol; The mass m1 of the first organic solvent, the mass m2 of the phosphorus-containing compound, the mass m3 of the bisphenol compound, and the mass m4 of 2,4-dimethyl-3-hydroxybenzocyclobutene satisfy the following condition: m1:(m2+m3+m4)=1800:(153.3+149.0+224.3).

[0099] The phosphorus-containing compound is phosphorus oxychloride; The acid-binding agent is trimethylamine; The type of bisphenol compound is 1,4-dihydroxybiphenyl; The first organic solvent is toluene; The catalyst is N,N'-dimethylformamide.

[0100] The polymerization reaction was carried out at a temperature of 60℃ for 11 hours.

[0101] The phosphorus-containing flame retardant has the molecular structure shown in Formula 1. , Formula 1, In Formula 1, the R1 group is ; The value of n satisfies: 0 < n ≤ 30, and the value of n is an integer.

[0102] Example 5

[0103] Compared to Example 1, the differences in this example are as follows, while the rest are the same: The phosphorus content in the phosphorus-containing flame retardant is 8.59% by mass.

[0104] The amount of phosphorus-containing compound n1 and the amount of acid-binding agent n2 satisfy: n1:n2 = 1 mol: 3.90 mol; The amount of catalyst n3 and the amount of phosphorus-containing compound n1 satisfy the following: n3:n1=0.0149mol:1mol; based on the mass of 1mol of phosphorus-containing compound being 153.3 parts by mass, the mass of the catalyst is 4.8 parts by mass.

[0105] The amounts of bisphenol compound n4 and 2,4-dimethyl-3-hydroxybenzocyclobutene n5 satisfy the following: n4:n5 = 0.75 mol: 1.60 mol; The mass m1 of the first organic solvent, the mass m2 of the phosphorus-containing compound, the mass m3 of the bisphenol compound, and the mass m4 of 2,4-dimethyl-3-hydroxybenzocyclobutene satisfy the following condition: m1:(m2+m3+m4)=1600:(153.3+103.6+256.3).

[0106] The phosphorus-containing compound is phosphorus oxychloride; The acid-binding agent is trimethylamine; The type of bisphenol compound is resorcinol; The first organic solvent is toluene; The catalyst is tetrabutylammonium bromide.

[0107] The polymerization reaction was carried out at a temperature of 60℃ for 11 hours.

[0108] The phosphorus-containing flame retardant has the molecular structure shown in Formula 1. , Formula 1, In Formula 1, the R1 group is ; The value of n satisfies: 0 < n ≤ 35, and the value of n is an integer.

[0109] Example 6

[0110] Compared to Example 1, the differences in this example are as follows, while the rest are the same: The phosphorus content in the phosphorus-containing flame retardant is 6.33% by mass.

[0111] The amount of phosphorus-containing compound n1 and the amount of acid-binding agent n2 satisfy: n1:n2 = 1 mol: 3.90 mol; The amount of catalyst n3 and the amount of phosphorus-containing compound n1 satisfy the following: n3:n1=0.0149mol:1mol; based on the mass of 1mol of phosphorus-containing compound being 153.3 parts by mass, the mass of the catalyst is 4.8 parts by mass.

[0112] The molar amounts of bisphenol compound n4 and 2,4-dimethyl-3-hydroxybenzocyclobutene n5 satisfy the following ratio: n4:n5 = 0.35 mol: 2.30 mol; The mass m1 of the first organic solvent, the mass m2 of the phosphorus-containing compound, the mass m3 of the bisphenol compound, and the mass m4 of 2,4-dimethyl-3-hydroxybenzocyclobutene satisfy the following condition: m1:(m2+m3+m4)=1600:(153.3+108.7+368.5).

[0113] The phosphorus-containing compound is phosphorus oxychloride; The acid-binding agent is trimethylamine; The type of bisphenol compound is tetramethylbisphenol A; The first organic solvent is toluene; The catalyst is tetrabutylammonium bromide.

[0114] The polymerization reaction was carried out at a temperature of 60℃ for 11 hours.

[0115] The phosphorus-containing flame retardant has the molecular structure shown in Formula 1. , Formula 1, In Formula 1, the R1 group is ; The value of n satisfies: 0 < n ≤ 19, and the value of n is an integer.

[0116] Example 7

[0117] The application of a phosphorus-containing flame retardant in copper-clad laminates, by weight, comprises the following raw materials: polyolefin resin: 73 parts, phosphorus-containing flame retardant obtained in Example 1: 27 parts, initiator: 0.15 parts, and filler: 45 parts. The second organic solvent is 78 parts by weight.

[0118] The methods for preparing copper-clad laminates include: S1. Polyolefin resin, phosphorus-containing flame retardant, initiator and filler are mixed in a second organic solvent to obtain a resin solution with a solid content of 65% by mass. S2. Glass fibers are sequentially impregnated and suspended in a resin solution to obtain flame-retardant glass fiber cloth; S3. Bake the flame-retardant treated fiberglass cloth to obtain a halogen-free flame-retardant semi-cured sheet; S4. Stack 10 layers of halogen-free flame-retardant semi-cured sheets to obtain a laminated material; S5. Attach copper foil to both sides of the laminate to obtain copper-clad laminate.

[0119] The baking temperature is 150℃, and the baking time is 6 minutes; The lamination process includes a pressurization section, a vacuum pressing section, and a hot pressing section. The final pressure of the pressurization section is 2.0 MPa; the vacuum degree of the vacuum pressing section is ≤50 torr, and the vacuum pressing time is 1.0 h; the temperature of the hot pressing section is 220℃, and the hot pressing time is 5 h.

[0120] The type of polyolefin resin is butadiene-styrene copolymer (Kreville Ricon 100). The initiator is dicumyl peroxide (Hongbaoli Group Co., Ltd.); The filler is silica (Jiangsu Lianrui DQ1040). The second organic solvent is butanone.

[0121] Example 8

[0122] Compared to Example 7, the differences in this example are as follows, while the rest are the same: The raw materials for the copper-clad laminate, by weight, include: polyolefin resin: 69 parts, phosphorus-containing flame retardant obtained in Example 2: 31 parts, initiator: 0.11 parts, and filler: 55 parts. The second organic solvent has a weight of 83 parts.

[0123] The type of polyolefin resin is butadiene-styrene copolymer (Kreville Ricon 100).

[0124] Example 9

[0125] Compared to Example 7, the differences in this example are as follows, while the rest are the same:

[0126] The raw materials for the copper-clad laminate, by weight, include: polyolefin resin: 65 parts, phosphorus-containing flame retardant obtained in Example 3: 35 parts, initiator: 0.13 parts, and filler: 50 parts. The second organic solvent has a weight of 81 parts.

[0127] The type of polyolefin resin is butadiene-styrene copolymer (Kreville Ricon 100).

[0128] Example 10

[0129] Compared to Example 7, the differences in this example are as follows, while the rest are the same: The raw materials for the copper-clad laminate, by weight, include: polyolefin resin: 61 parts, phosphorus-containing flame retardant obtained in Example 4: 39 parts, initiator: 0.10 parts, and filler: 60 parts. The second organic solvent has a weight of 86 parts.

[0130] The type of polyolefin resin is butadiene polymer (Kreville Ricon 134).

[0131] Example 11

[0132] Compared to Example 7, the differences in this example are as follows, while the rest are the same: The raw materials for the copper-clad laminate, by weight, include: polyolefin resin: 58 parts, phosphorus-containing flame retardant obtained in Example 5: 42 parts, initiator: 0.12 parts, and filler: 57 parts. The second organic solvent has a weight of 84 parts.

[0133] The type of polyolefin resin is butadiene polymer (Kreville Ricon 134).

[0134] Example 12

[0135] Compared to Example 7, the differences in this example are as follows, while the rest are the same: The raw materials for the copper-clad laminate, by weight, include: polyolefin resin: 55 parts, phosphorus-containing flame retardant obtained in Example 6: 45 parts, initiator: 0.09 parts, and filler: 49 parts. The second organic solvent is 80 parts by weight.

[0136] The type of polyolefin resin is butadiene polymer (Kreville Ricon 134).

[0137] Comparative Example 1

[0138] Compared to Example 7, the differences in this comparative example are as follows, while the rest are the same: The raw materials for copper-clad laminate, by mass, include: polyolefin resin: 85 parts, phosphorus-containing flame retardant obtained in Example 1: 15 parts, filler: 52 parts, and initiator: 0.2 parts.

[0139] The type of polyolefin resin is polybutadiene resin.

[0140] The temperature of the hot pressing section is 210℃, and the hot pressing time is 5 hours.

[0141] Comparative Example 2

[0142] Compared to Example 8, the differences in this comparative example are as follows, while the rest are the same: In Example 2, 2,4-dimethyl-3-hydroxybenzocyclobutene was replaced with 4-hydroxybenzocyclobutene. The synthesized phosphorus-containing flame retardant was then used in the preparation of copper-clad laminates.

[0143] By weight, the raw materials for copper clad laminate include: polyolefin resin: 60 parts, synthetic phosphorus-containing flame retardant: 40 parts, filler: 49 parts, and initiator: 0.2 parts.

[0144] The type of polyolefin resin is polybutadiene resin.

[0145] The temperature of the hot pressing section is 210℃, and the hot pressing time is 5 hours.

[0146] Comparative Example 3

[0147] Compared to Example 9, the differences in this comparative example are as follows, while the rest are the same: In Example 2, 2,4-dimethyl-3-hydroxybenzocyclobutene was replaced with 2,5-dihydroxyphenol. The synthesized phosphorus-containing flame retardant was then used in the preparation of copper-clad laminates.

[0148] By weight, the raw materials for copper clad laminate include: polyolefin resin: 60 parts, synthetic phosphorus-containing flame retardant: 40 parts, filler: 57 parts, and initiator: 0.2 parts.

[0149] The type of polyolefin resin is polybutadiene resin.

[0150] The temperature of the hot pressing section is 220℃, and the hot pressing time is 7 hours.

[0151] Relevant experimental and effect data: The copper-clad laminate products obtained from each embodiment and comparative example were collected, and the performance of these copper-clad laminate products was tested. The results are shown in Table 1.

[0152] Table 1 Performance parameters of copper clad laminate products in various embodiments and comparative examples

[0153] As shown in Table 1, the high heat resistance and low water absorption reactive phosphorus flame retardant provided in this application embodiment completely breaks the contradiction of "the trade-off between flame retardancy and water absorption, heat resistance and dielectric properties" existing in traditional phosphorus flame retardants through the triple molecular design of "steric shielding hydrophilic groups + reactive cross-linking locking system + hydrophobic skeleton reducing polarity". Ultimately, it achieves a comprehensive improvement in the performance of copper clad laminate: flame retardancy reaches UL94 V0 level, high heat resistance and high dimensional stability, excellent high frequency dielectric properties, and water absorption rate as low as 0.05% to 0.08%, perfectly solving the water absorption problem of phosphorus flame retardants.

[0154] Compared to Example 7, Comparative Example 1 used a lower amount of phosphorus-containing flame retardant. Although it could improve the heat resistance, mechanical properties and flame retardant properties of the copper clad laminate to some extent, the amount of phosphorus-containing flame retardant added was too low to improve the flame retardant properties of the copper clad laminate to the UL94 V0 level.

[0155] Compared to Example 8, Comparative Example 2 uses benzocyclobutene as the end-capping structure, which makes it difficult for the phosphorus-containing flame retardant to form a dense steric barrier around the polar phosphorus oxygen group through the methyl group. As a result, the copper-clad laminate obtained in Comparative Example 2 has good heat resistance and mechanical properties, but low water absorption and dielectric properties.

[0156] Compared to Example 9, Comparative Example 3 uses a phosphorus-containing flame retardant that does not contain multiple methyl steric hindrances or benzocyclobutene groups. Although this can impart halogen-free flame retardant properties and low water absorption to the copper-clad laminate, the absence of benzocyclobutene groups in the phosphorus-containing flame retardant makes it difficult for the polyolefin resin and the phosphorus-containing flame retardant to react, thus failing to improve the heat resistance, dimensional stability, and peel strength of the copper-clad laminate.

[0157] In summary, this application provides a high-heat-resistant, low-water-absorption reactive phosphorus-containing flame retardant. Through multi-dimensional synergistic design of its molecular structure, this phosphorus-containing flame retardant comprehensively improves the overall performance of copper-clad laminates (CCLs) while fundamentally solving the water absorption problem inherent in phosphorus-based flame retardants. Therefore, this phosphorus-containing flame retardant provides excellent halogen-free flame retardant properties and exhibits low water absorption. Furthermore, the benzocyclobutene-based active groups in this phosphorus-containing flame retardant can undergo cross-linking polymerization with polyolefin resins to form a uniform and dense cross-linked structure. This results in CCLs prepared using this phosphorus-containing flame retardant exhibiting good heat resistance, low water absorption, low dielectric properties, and low dielectric loss characteristics, meeting the high-frequency and high-speed requirements of printed circuit boards.

[0158] In addition, the phosphorus-containing flame retardant with high heat resistance and low water absorption provided in this application embodiment also has the following advantages: (1) The phosphorus-containing flame retardant has a high phosphorus content. These phosphorus elements decompose during the combustion stage of the copper-clad laminate to produce acidic substances such as phosphoric acid and metaphosphoric acid, which catalyze the dehydration and carbonization of the resin of the copper-clad laminate to form a dense and stable carbon layer. These carbon layers can effectively isolate oxygen and heat transfer. Therefore, only a small amount needs to be added to make the copper-clad laminate reach the UL94 V0 level and meet the safety requirements of high-frequency and high-speed printed circuit boards.

[0159] (2) The phosphorus-containing flame retardant contains four or more benzocyclobutene groups, which can undergo polymerization reaction with unsaturated resin (polyolefin resin) to form a cross-linked structure, ensuring long-term stability of flame retardant performance; at the same time, the rigid structures such as benzene ring, biphenyl ring, and naphthalene ring contained in the phosphorus-containing flame retardant molecule can significantly enhance the heat resistance and dimensional stability of the cured resin.

[0160] (3) The phosphorus-containing flame retardant contains a methyl structure in its molecular structure, which can increase the steric hindrance around the phosphorus oxygen in the phosphorus-containing flame retardant molecule, reduce the polarity of the phosphorus-containing flame retardant molecular structure and prevent the phosphorus oxygen from combining with water molecules, thereby achieving the low water absorption and low dielectric loss performance of the phosphorus-containing flame retardant.

[0161] (4) Both the phosphorus-containing flame retardant and the polyolefin resin used in the copper-clad laminate have low molecular polarity, resulting in excellent compatibility and the formation of a uniform cross-linked structure. This cross-linked structure imparts a uniform appearance, excellent heat resistance, and stable dimensions to the copper-clad laminate. Furthermore, the copper-clad laminate formed using this phosphorus-containing flame retardant exhibits excellent dielectric properties, with a dielectric constant as low as 2.59 to 2.67 at 10 GHz and a dielectric loss of only 0.0010 to 0.0011, making it suitable for high-frequency signal transmission requirements.

[0162] In addition, the application of a phosphorus-containing flame retardant in copper-clad laminates provided in this application results in copper-clad laminates with excellent overall performance: a dielectric constant as low as 2.59 to 2.67 at 10 GHz, a dielectric loss of only 0.0010 to 0.0011, a glass transition temperature of 244°C to 263°C, a peel strength of 1.43 N / mm to 1.51 N / mm, a flame retardant performance as high as UL94 V0, and a water absorption rate of 0.05% to 0.08%.

[0163] Furthermore, the application of a phosphorus-containing flame retardant in copper-clad laminates provided in this application is simple in its overall process, requires no special equipment, and the prepared copper-clad laminate is suitable for the field of high-frequency and high-speed printed circuit boards, which can meet the high-performance requirements of industries such as 5G communication and artificial intelligence for copper-clad laminates, and has significant practicality and industrialization prospects.

[0164] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A highly heat-resistant, low-water-absorption reactive phosphorus-containing flame retardant, characterized in that, The phosphorus-containing flame retardant has the molecular structure shown in Formula 1. ， Formula 1, In Formula 1, the R1 group includes , , , , , , , , , , , , , and At least one of them; The value of n satisfies: 0 < n ≤ 50, and the value of n is an integer.

2. The phosphorus-containing flame retardant according to claim 1, characterized in that, The phosphorus content in the phosphorus-containing flame retardant is 6.3% to 9.1% by mass.

3. A method for preparing the phosphorus-containing flame retardant according to claim 1 or 2, characterized in that, The method includes: Phosphorus oxychloride, an acid-binding agent, and a first organic solvent are mixed to obtain the reaction raw materials; The bisphenol compound, 2,4-dimethyl-3-hydroxybenzocyclobutene, catalyst and the reactants were subjected to a polymerization reaction to obtain the reaction product; The reaction product was washed with pure water to obtain a washed product; The washing product was subjected to vacuum distillation to obtain a phosphorus-containing flame retardant.

4. The method according to claim 3, characterized in that, The amount of the phosphorus-containing compound, n1, and the amount of the acid-binding agent, n2, satisfy: n1:n2 = 1:(3.05 to 4.50); ​​and / or The amount of the catalyst n3 and the amount of the phosphorus-containing compound n1 satisfy: n3:n1 = (0.01 to 10.00):1; and / or The molar amounts n4 of the bisphenol compound and n5 of the 2,4-dimethyl-3-hydroxybenzocyclobutene satisfy: n4:n5 = (0.35 to 0.80):(1.6 to 2.3); and / or The mass m1 of the first organic solvent, the mass m2 of the phosphorus-containing compound, the mass m3 of the bisphenol compound, and the mass m4 of the 2,4-dimethyl-3-hydroxybenzocyclobutene satisfy the following: m1:(m2+m3+m4)=(2.5 to 6):

1.

5. The method according to claim 3, characterized in that, The acid-binding agent includes at least one of sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, sodium bicarbonate, potassium bicarbonate, tetrahydrofuran, trimethylamine, triethylamine, sodium acetate, and potassium acetate; and / or The bisphenol compounds include at least one selected from hydroquinone, resorcinol, bisphenol A, bisphenol C, bisphenol F, tetramethylbisphenol A, tetramethylbisphenol F, 4,4'-dihydroxybiphenyl, tetramethylbiphenyl, hexamethylbiphenyl, 1,5-naphthoquinone, 1,4-dihydroxynaphthol, and 1,6-dihydroxynaphthol; and / or The first organic solvent includes at least one of toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexane, and n-hexane; and / or The catalysts include at least one of the following: tetrabutylammonium bromide, benzyltriethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, crown ether, polyethylene glycol, acetonitrile, N,N'-dimethylformamide, and N,N'-dimethylacetamide.

6. The method according to claim 3, characterized in that, The polymerization reaction is carried out at a temperature of 50°C to 60°C for a duration of 8 to 12 hours; and / or The temperature of the early mixing stage of the polymerization reaction is ≤45℃.

7. The application of the phosphorus-containing flame retardant as described in claim 1 or 2 in copper-clad laminates, characterized in that, The raw materials of the copper-clad laminate, by weight, include: polyolefin resin: 55 to 73 parts, phosphorus-containing flame retardant as described in claim 1 or 2: 27 to 45 parts, initiator: 0.03 to 0.25 parts, and filler: 45 to 60 parts; wherein the sum of the weight parts of the polyolefin resin and the phosphorus-containing flame retardant is 100.

8. The application according to claim 7, characterized in that, The method for preparing the copper-clad laminate includes: The polyolefin resin, the phosphorus-containing flame retardant, the initiator, and the filler are mixed in a second organic solvent to obtain a resin solution; Glass fibers are sequentially impregnated and suspended in the resin solution to obtain flame-retardant glass fiber cloth. The flame-retardant treated glass fiber cloth is baked to obtain a halogen-free flame-retardant semi-cured sheet. The halogen-free flame-retardant semi-cured sheets are stacked to obtain a laminated material; Copper foil is attached to both sides of the laminate to obtain a copper-clad laminate.

9. The application according to claim 8, characterized in that, The baking temperature is 130°C to 170°C, and the baking time is 4 min to 7 min; and / or The lamination process includes a pressurization section, a vacuum pressing section, and a hot pressing section. The final pressure of the pressurization section is 0.2 MPa to 4.0 MPa. The vacuum degree of the vacuum pressing section is ≤50 torr, and the vacuum pressing time is 0.5 h to 1.0 h. The temperature of the hot pressing section is 200 °C to 220 °C, and the hot pressing time is 4 h to 8 h.

10. The application according to claim 8, characterized in that, The polyolefin resins include at least one of the following: butadiene polymers, butadiene-styrene copolymers, butadiene-styrene-monobutene terpolymers, divinylbenzene polymers, and divinylbenzene-monobutene copolymers; and / or The initiator includes at least one of dicumyl peroxide, di-tert-butyl peroxide, and tert-butyl peroxide; and / or The filler material includes at least one of the following: silica, montmorillonite, magnesium oxide, aluminum oxide, mica powder, barium sulfate, kaolin, silicon nitride, boron nitride, zirconium oxide, aluminum nitride, graphite, titanium dioxide, talc, and iron oxide; and / or The second organic solvent includes at least one of acetone, butanone, cyclohexanone, methyl isobutyl ketone, toluene, propylene glycol monomethyl ether, and propylene glycol methyl ether acetate.

Images